Nano-Droplet Generators

N.C. Emley and J. BokorUC Berkeley, US

Keywords:microfluidics, MEMS resonators, droplet formation

Abstract:This poster describes the current status of a project to fabricate a monolithic, micro-machined device able to generate sub-micron diameter fluidic droplets. These droplet-on-demand (DoD) devices are important for a wide range of maskless lithography, rapid prototyping, spotting, and biological analysis technologies. A MEMS-based flexure plate, suspended membrane actuator was chosen, rather than a thermal-bubble method, as it can achieve the requisite pressures for such small droplets. Mechanical actuation does not damage the fluid or suspended particle solution, as would happen in thermal-bubble where the fluid is boiled. Advances in sol-gel-derived lead zirconate titanate (PZT) thin film deposition techniques allow for wafer scale integration of PZT as the active layer of the flexure plate. LPCVD dielectrics serve as structural underlayers for the PZT and a suspended membrane will be formed by a backside through-etch of the Si handle. Fast (~10 MHz) and uniform deflection of the membrane is crucial to produce sufficient pressures for droplet generation, which then requires their fundamental-mode acoustic resonant frequency be as high as possible. Acoustic resonance is tunable through choice of membrane diameter, geometry, thickness, stress, and layering composition. We report the current status of device fabrication and development.

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